RiverWare User’s Group Meeting

Pecos River Adjudication Settlement: Application of an

Integrated Surface and Ground Water Modeling System

June 18, 2003

Presentation Outline

• Overview of Pecos River Institutions / Operational Policies

• Adjudication Settlement: Problems and Solutions

• The Pecos River DSS• Evaluating the Settlement Terms• Conclusions

Institutions and Operations

• Pecos River Compact and Amended Decree (New Mexico / Texas)

• Water Rights - Prior Appropriation Doctrine; adjudication and administration

• ESA operations for Pecos Bluntnose Shiner• 2 NEPA EIS programs• Carlsbad Project (reservoir operations, GW

diversions)• Other diverters (FSID, river pumpers, M&I, etc)• PVACD groundwater diversions

Major Irrigators, Physical Features, and Critical Resource Locations in the Pecos Basin

Carlsbad Irrigation

District

Fort Sumner Irrigation District

Santa Rosa Reservoir

Brantley Reservoir

NM - TX State Line / Pecos River Compact

Pecos Valley Artesian Conservancy District

USGS gage PR @ Acme

Sumner Reservoir

Pecos Adjudication Settlement

• Parties: PVACD, CID, NM ISC, United States

• Purpose:– Ensure long-term compliance with the Pecos River

Compact and Amended Decree– Avoid need for priority administration of water rights– Maintain or enhance water supplies / aquifer storage

levels• Proposal:

– NM ISC purchases water rights / land from PVACD and CID

– CID water delivered to state line for Compact deliveries– PVACD lands retired, water provides augmentation

supply when needed

Pecos Adjudication Settlement - Evaluation of

the Proposal• Use existing modeling tools to evaluate and

refine Settlement terms.• Pecos River DSS integrates RiverWare, two

MODFLOW models, an accounting model, and numerous I/O tools.

• “Rules” simulate baseline conditions and proposed actions.

• Various resource indicators used to quantify “value” of actions by comparing baseline and Settlement model results.

Approximate Spatial Domain of Pecos Decision Support System Models

Pecos River RiverWare

Model

Roswell Artesian Basin Groundwater Model

Carlsbad Area Groundwater

Model

Red Bluff Accounting Model

Santa Rosa Reservoir

Brantley Reservoir

NM / TX State Line

Pecos River RiverWare Model• Rule-based

simulation of Pecos River hydrology and reservoir operations from Santa Rosa Reservoir to Avalon Dam

• USBR, Tetra Tech, Hydrosphere, Pecos HWG

Roswell Artesian Basin Groundwater Model

• Calibrated MODFLOW model of groundwater flow in Roswell Artesian Basin, in both the deep artesian and shallow alluvial aquifers

• Simulates areal and stream recharge, pumping stress, Pecos River - groundwater interaction

• Predicts base inflows to the Pecos River

• Amy Lewis, NM SEO (Eric Keyes), SSPA, Hydrosphere

Carlsbad Area Groundwater Model

• MODFLOW model that simulates groundwater flow in the Capitan Reef and overlying alluvial aquifer in the Pecos River Basin from Lake Avalon to the Malaga Bend

• Simulates surface-water irrigation, groundwater diversions, losses, and return flows

• Predicts base inflows to the Pecos River

• Amy Lewis, NM SEO (Peggy Barroll), Intera/Hydrosphere

Red Bluff Accounting Model• Computes Monthly and Annual Flows at

Red Bluff– Historical (Calibration)– Current Conditions (Alternative Evaluation)

• Red Bluff Flow = Resource Indicator– Evaluation of Policy Alternatives– Interstate Compact Implications

• Calculation of Calibration Targets for CAGW

Data Processing Tool (DPT)• Input/Output for

Models• Data Archiving/

Metadata• Alternative

Evaluation and ArchivingRiverWare

Data ProcessingTool RBAM

CAGWRABGW

Settlement Modeling Challenges

• CID Allotment based on surface water supply (RiverWare)

• Augmentation pumping in Roswell Basin conditioned on CID water supply: pumping occurs when CID supplies short of 90Kaf; up to 35Kaf/year, 100 Kaf per 5-year accounting period (Feedback from RiverWare to RABGW model)

• Compact credit thresholds computed by Red Bluff model drive RiverWare rules for water deliveries (Feedback from RBAM, via CAGW, to RiverWare):– Carlsbad Irrigation District allotment and distribution – Delivery of water to Texas

RiverWareRes Ops

Water DeliveryData Processing

Tool (DPT)

Red BluffAcct Model

Pecos Compact

CAGWSurface water diversions

Supplemental GW pumping

RABGWLand RetirementAug. Pumping

Pecos Decision Support System: Model Linkages

Feedback Loops: Compact deliveries drive reservoir ops CID Supply drives Roswell augmentation pumping

Settlement Model Implementation

• Baseline model w/ Settlement Rules• Iterate between RiverWare and RABGW to

determine total augmentation pumping• Sensitivity analysis in Carlsbad GW model;

results used by RiverWare to estimate compact credit

• Simulate basin operations to state line and verify estimates used in RiverWare

Evaluation of Settlement Terms

• Avoid priority administration (50,000 AF Supply on March 1)

• Meet Compact delivery requirements (Stateline flows and Compact accounting)

• Maintain or enhance CID water supply• Maintain or enhance Roswell basin aquifer

storage levels

Resource Indicator: Roswell Basin Aquifer Storage

Derived from RABGW ModelLayer 1 RABGW Model, Alluvial Aquifer

Predevelopment Storage ~ 17.3 million afSimulation Start Date = Jan 1, 2000

-18.0%

-17.5%

-17.0%

-16.5%

-16.0%

-15.5%

-15.0%

-14.5%

-14.0%

-13.5%

-13.0%

-12.5%

-12.0%

1 4 7 10 13 16 19 22 25 28

Year

No

rmali

zed

Sto

rag

e D

efi

cit

(af)

Baseline

Settlement

Resource Indicator: CID Supply and Sources - March 1 Supply - Settlement

ScenarioCID Surface Water Supply - March 1

0

20000

40000

60000

80000

100000

120000

140000

1 4 7 10 13 16 19 22 25 28

Year

To

tal

Su

pp

ly D

eli

ve

rab

le a

t A

va

lon

(A

cre

-fe

et)

Augmentation from PVACD Wells

Pecos River Native Flow

Resource Indicator: Compact Obligations and Departures: Cumulative Departure

Cumulative Compact Departure from Obligation Initial Condition = January 1, 2000

-200

-150

-100

-50

0

50

100

150

200

250

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Year

To

tal

Dep

art

ure

(T

ho

usan

ds o

f A

cre

-Feet)

Baseline

Settlement

Average Departure = (-2,950 af/yr)

Average Departure = 6,430 af/yr)

Settlement Gains to Stateline Flows Sources of Additional Stateline Flow under Proposed Settlement

-30000

-20000

-10000

0

10000

20000

30000

1 4 7 10 13 16 19 22 25 28

Year

So

urc

e F

low

(A

cre

-fee

t)

0

50000

100000

150000

200000

250000

300000

ISC Release of CID Water Rights

Conservation Spills

Baseflow Gains from CID Return Flows

Cumulative Gain in Stateline Flow

What’s Next?

• Settlement parties signed agreement in spring 2003

• Ongoing applications of PRDSS:– Identification/evaluation of candidate lands

for retirement (PVACD and CID)– FWS B.O. on Pecos Bluntnose Shiner– Identification, evaluation, and refinement of

alternatives for ongoing Carlsbad Project EIS– Annual Carlsbad Project water accounting

(Reclamation)

Settlement Model Assumptions

(example)• Distribution of water from 6,000 acres of CID land purchased by

ISC conditioned on cumulative Compact credit and current water supply (ISC water “yield” = 1.176 x allotment):– If CID supply < 50Kaf on March 1, ISC water realloted to CID– If credit < 50Kaf, deliver ISC water to stateline 5x annually– if 50Kaf < credit < 115 Kaf, AND current supply > 90Kaf, ISC gets all

water > 90 Kaf, up to 24,696 af (3.5x1.176x6000). Beyond 114,696 af, water is alloted to all 25,055 acres equally.

– if 50Kaf < credit < 115 Kaf, AND current supply < 90Kaf, ISC shall make its CID water available for re-distribution to CID irrigators up to 3.5 af/acre (90Kaf)

– if credit > 115 Kaf, ISC shall make its CID water available for re-distribution to CID irrigators up to decreed limit (3.697 af/acre); IF CID irrigators have full allotment, excess water to be held over in storage

RiverWare Rulebased Simulation

• Operational policy is simulated using RiverWare rules

• Management alternatives can be readily evaluated

RiverWare - Implementation• USBR began work in 1991 following FWS B.O.

– Data collection program– Daily timestep model of river/reservoir operations– Need to evaluate operational alternatives

• HWG review / enhancement process started 1999– Evaluation of data and methods (side inflows,

routing, gain/loss, evaporation, bank storage, etc.)– Development of “Ruleset” representing current

reservoir operations policy

• Relevance to Settlement:– Impact of reservoir operations and physical

processes on Texas deliveries and CID allotments– Long-term water supply implications

Roswell Artesian Basin Groundwater Model -

Implementation• RABGW “roots”: Lewis model (1991-

1995); Keyes and SSPA enhancements• Calibrated based on 1967-2000 heads,

1967-2000 pumping data, and 67-2000 Pecos River base inflows

• Relevance to NEPA process:– Interrelationships between surface water

deliveries, well pumping, and climatic drivers– Direct impact on Pecos River flows from

Acme to Artesia

Carlsbad Area Groundwater Model - Implementation

• CAGW “roots”: Lewis model (1991); Bjorklund and Motts survey (1959)

• Updated and enhanced by NM OSE and Intera

• Relevance to Settlement:– Interrelationships between surface water

deliveries, supplemental well pumping, and return flows

– Direct impact on Pecos River flows below Avalon (and thus stateline deliveries)

RBAM - Implementation

• Mass-balance calculation of Red Bluff flows – Input includes RiverWare and CAGW outputs

via DPT

• Monthly and annual surface-water budget for the Avalon to state-line reach

• Relevance to Settlement:– Pecos Compact obligations and departures– Impacts of potential changes in reservoir

operation and CID irrigation supply sources on stateline deliveries

DPT - Implementation

• Coupling of RiverWare, CAGW, and RBAM• RiverWare post-processing

– CID diversion, Avalon seepage and Avalon releases– Time-step conversion

• CAGW pre- and post-processing– Determination of CID supplemental well pumping

entitlements– Computation of Pecos River gains below Avalon

• Archiving– Data– Policy alternatives